The present application is based on and claims priority from Japanese Patent Application 2000-183473 filed Jun. 19, 2000, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a fuel injection device for an internal combustion engine.
2. Description of the Related Art
In order to reduce noxious components of engine combustion exhaust gas, it is important to atomize fuel injected from a fuel injection device. For example, fuel is heated and decompressed so as to be evaporated. This is very effective, especially, when an engine is started at a cold temperature.
One of an inexpensive way of heating fuel is to heat a portion around the fuel injection device. However, this necessitates large electric power and is not very effective.
Another way of heating is to put a heating element directly in fuel. This necessitates sealing of electric wires, which is very troublesome.
Therefore, a main object of the invention is to provide an improved fuel injection device having a highly efficient heating arrangement that does not necessitate sealing of electric wires.
A fuel injection device according to a feature of the invention includes a cylindrical valve housing, a valve needle and a ceramic heater. The valve housing has a fuel inlet at an end, a first fuel passage, a second fuel passage, a valve seat and a nozzle hole at the other end. The valve needle is disposed between the first and second fuel passages inside the valve housing. The valve needle has a hollow portion connected to the first fuel passage and a plurality of fuel apertures connecting the hollow portion and the second fuel passage, a head portion to be seated on or unseated from the valve seat thereby intermittently injecting fuel through the nozzle hole. The ceramic heater is disposed around the valve housing down stream of the plurality of fuel apertures and upstream of the valve seat to directly heat a portion of the valve housing.
The nozzle needle may have a bulging portion opposite the ceramic heater to narrow the cross-section of the second fuel passage, thereby effective by heating fuel to be injected.